Blood pressure depends on two factors:

BP = cardiac output x peripheral resistance

It is regulated by controlling each of these simultaneously by autonomic nervous reflexes.
These are baroreceptor reflexes:

• the carotid sinus reflex
• the aortic arch reflex

Additional Information

Carotid Sinus Reflex
This reflex depends on baroreceptors located in the walls of the carotid arteries at the carotid bifurcation. The carotid sinus is a small dilation just above where the carotid artery divides into internal and external carotid arteries.

Aortic Arch Reflex
This reflex depends on baroreceptors in the wall of the arch of the aorta.